/*
 * Copyright 2004-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package susano.presen.validator;

import java.util.Map;

import susano.presen.util.ApplicationMessage;

/**
 * A validator for a required value.
 *
 * @author tanaka.akira.2006
 * @version $Id: RequiredValidator.java 220 2009-10-13 08:50:15Z tanaka.akira.2006 $
 */
public class RequiredValidator extends AbstractValidator {

	/**
	 * The instance.
	 */
	public static RequiredValidator INSTANCE = new RequiredValidator();

	/**
	 * Constructor.
	 */
	public RequiredValidator() {
		super();
	}

	/**
	 * Constructor.
	 *
	 * @param message
	 *            the error message
	 */
	public RequiredValidator(String message) {
		super(message);
	}

	public String validate(Map<String, Object> parameters, String name) {
		Object value = parameters.get(name);
		if (value == null || "".equals(value)) {
			if (message != null) {
				return message;
			}
			return ApplicationMessage.get("validator.required", getLabel(name));
		}
		return null;
	}
}